Assembly system utilizing a flat, elastic locking element

ABSTRACT

The invention relates to an assembly system including a member made of at least a first material including a staff and a shoulder, the staff of the member being received in an aperture of a part made of a second material having little or no plastic domain. According to the invention, the assembly system includes a locking element made of a third material arranged to elastically attach the part between the shoulder of said member and the locking element and in that the locking element is a washer whose internal wall radially grips the staff of said member and whose peripheral portion exerts an elastic radial force vertical to the shoulder of said member in order to secure the assembly of the member-part-locking element.

This application claims priority from European Patent Application No.13187833.2 filed Oct. 9, 2013, the entire disclosure of which is herebyincorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to an assembly system utilising a substantiallyflat, elastic locking element making it possible to assemble a part madeof a material which has no usable plastic domain, i.e. with a verylimited plastic domain, to a member comprising a different type ofmaterial.

BACKGROUND OF THE INVENTION

Current assemblies including a silicon-based part are generally securedby bonding. This type of operation requires extremely delicateapplication which makes it expensive.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome all or part of theaforecited drawbacks by providing an adhesive-free assembly which cansecure a part made of a material with no plastic domain to a membercomprising a ductile material, such as, for example, a metal or metalalloy.

To this end, the invention relates to an assembly system including amember made of at least a first material including a staff, a shaft oran arbor and a shoulder, the shaft of the member being received in theaperture of a part made of a second material, characterized in that theassembly system includes a locking element made of a third materialarranged to elastically attach the part between the shoulder of saidmember and the locking element, and in that the locking element is awasher whose internal wall radially grips the shaft of said member andwhose peripheral portion exerts an elastic axial force vertical to theshoulder of said member in order to secure the assembly of themember-part-locking member.

This configuration advantageously enables the member-part-lockingelement assembly to be secured without adhesive bonding to an ordinary,precision controlled member, while ensuring that the part is not subjectto destructive stresses, even if it is formed, for example, from asilicon-based material. Indeed, the Applicant was surprised to be ableto secure the member-part-locking element assembly, particularly inrelative rotation, with such great structural simplicity, sincepreconceived ideas as to the mechanical resistance of parts made fromsilicon-based materials have, to date, required that no axial force isapplied to a part made of material having little or no plastic domain.

In accordance with other advantageous features of the invention:

-   -   the third material includes a metal or a metal alloy whose        resistance to relaxation, after 10,000 hours at a temperature of        70° C. is equal to at least 50% of the applied force        representing 75% of the stress necessary to obtain 0.2% plastic        deformation of the third material in order to maintain the        secure assembly of the member-part-locking element;    -   the third material includes copper, brass, nickel silver (also        called “maillechort” or “new silver”), ARCAP alloy, Pfinodal        alloy, Spinodal alloy, Durnico alloy, Durimphy alloy, Cu—Be        alloy and/or 20AP steel;    -   the height to width ratio of the locking element in        cross-section in an axial plane is between 0.1 and 5;    -   the locking element is chamfered to prevent any damage to the        second material;    -   the second material is silicon-based such as silicon, quartz,        silicon oxide, silicon nitride or silicon carbide;    -   said at least one first material includes a metal or a metal        alloy;    -   the shaft and the shoulder are in one piece.

Further, the invention relates to a timepiece, characterized in that itincludes at least one assembly system according to any of the precedingvariants, the part with no plastic domain being able to be a wheel,pallets or a balance spring.

Finally, the invention relates to a method of manufacturing an assemblysystem including the following steps:

-   -   a) forming a member made of at least a first material including        a staff, an arbor or a shaft and a shoulder, a part made of a        second material with an aperture and a locking element in the        form of a washer made from a third material and whose hole is        smaller than the staff of shaft of said member;    -   b) inserting the shaft of said member freely into the aperture        of the part;    -   c) placing the shaft against the hole in the locking element and        forcibly sliding the locking element against the shaft using a        tool to deform the locking element so that the peripheral        portion of the locking element is the closest to the part;    -   d) stopping and removing said tool when a predefined force less        than the yield strength of the third material is reached between        the tool and the shoulder of said member.

This method advantageously makes it possible to secure themember-part-locking element assembly in a simple, elastic manner andwith no possible relative movement. Indeed, advantageously according tothe invention, only one locking element is provided and deformed toachieve purely elastic peripheral clamping. It is easily understood thata method of this type makes it possible to secure the assembly of themember-part-locking element while adapting to manufacturing variationsin the various components.

Finally, surprisingly, the axial stress exerted by the peripheralportion of the locking element in the method does not cause any breakageof the second material having little or no plastic domain. Thistechnical advantage makes it possible to considerably simplify theassembly of parts having little or no plastic domain onto a pivotingstaff. It is understood in particular that it is not necessary toprovide any adhesive, additional locking cap or complementary covershapes to secure the parts to each other particularly as regardsrelative movements about the axis of rotation of the pivoting shaft.

In accordance with other advantageous features of the invention:

-   -   step d) is stopped when the force applied by said tool is        comprised between 20% and 90% of the yield strength of the third        material;    -   the third material includes a metal or a metal alloy whose        resistance to relaxation, after 10,000 hours at a temperature of        70° C. is equal to at least 50% of the force applied in step d)        representing 75% of the stress necessary to obtain 0.2% plastic        deformation of the third material in order to maintain the        secure assembly of the member-part-locking element;    -   the third material includes copper, brass, nickel silver (also        called “maillechort” or “new silver”), ARCAP alloy, Pfinodal        alloy, Spinodal alloy, Durnico alloy, Durimphy alloy, Cu—Be        alloy and/or 20AP steel;    -   the height to width ratio of the locking element in        cross-section in an axial plane is between 0.1 and 5;    -   the locking element is chamfered to prevent any damage to the        second material;    -   the second material is silicon-based such as silicon, quartz,        silicon oxide, silicon nitride or silicon carbide;    -   said at least first material includes a metal or a metal alloy;    -   the part is a timepiece wheel set, a timepiece pallets or a        timepiece balance spring.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages will appear clearly from the followingdescription, given by way of non-limiting illustration, with referenceto the annexed drawings, in which:

FIG. 1 is a perspective view of a locking element according to theinvention;

FIG. 2 is a cross-section in an axial plane of a locking element of FIG.1;

FIG. 3 is a graphical representation of the force applied in the methodaccording to the axial position of the tool exerting said force;

FIGS. 4 to 8 are schematic cross-sections of successive steps of themethod according to the invention;

FIGS. 9 and 10 are partial, schematic views of a timepiece movementincluding assembly systems according to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As explained above, the invention relates to a system of assembling apart, made of a material having no usable plastic domain, i.e. with avery limited plastic domain, to a member comprising a different type ofmaterial.

This assembly system was devised for applications within the field ofhorology. However, other domains may very well be envisaged, such as,notably aeronautics, jewellery, the automobile industry or tableware.

In the field of horology, this assembly is made necessary by theincreasing part played by fragile materials such as silicon-basedmaterials like doped or non-doped single crystal (or polycrystalline)silicon, silicon oxide, such as quartz or silica, single crystal orpolycrystalline corundum or, more generally, alumina, silicon nitrideand silicon carbide. By way of example, it is possible to envisageforming the balance spring, balance, pallets, bridges or even wheelsets, such as the escape wheels, completely or partially from a base offragile materials.

However, always being able to use ordinary steel staffs, shafts orarbors, the fabrication of which has been mastered, is a constraintwhich is difficult to reconcile with the use of parts having no plasticdomain. Indeed, when tests were carried out, it was impossible to drivein a steel staff and this systematically broke fragile parts, i.e. thosewith no usable plastic domain. For example, it became clear that theshearing generated by the metallic staff entering the aperture in asilicon component systematically breaks the component.

This is why the invention relates to an assembly system 1, 101, 121, 201including a member 3, 103, 123, 203 made of at least a first materialincluding a staff 2, 102, 122, 202 and a shoulder 4, staff 2 of themember being received in the aperture 6 of a part 5, 105, 205 made of asecond material having little or no plastic domain.

It is thus understood that staff 2, 102, 122, 202 and shoulder 4 may bein a single piece using a single first material or that staff 2, 102,122, 202 and shoulder 4 of member 3, 103, 123, 203 may be formed ofseveral materials and/or several portions.

Advantageously according to the invention, the assembly system 1, 101,121, 201 includes a locking element 9, 109, 129, 209 made of a thirdmaterial arranged to elastically attach part 5, 105, 205 betweenshoulder 4 of member 3, 103, 123, 203 and locking element 9, 109, 129,209. As better illustrated in FIG. 8, advantageously according to theinvention, part 5 is clamped against shoulder 4 of member 3 by theelastic force of locking element 9. The simplicity of assembly system 1,101, 121, 201 according to the invention, which requires no adhesive,additional locking cap, complementary cover shapes or plasticdeformation such as creep, is immediately clear.

Preferably according to the invention, locking element 9, 109, 129, 209is a washer whose internal wall 10 radially grips staff 2, 102, 122, 202of member 3, 103, 123, 203 and whose peripheral portion 13 exerts anelastic axial force vertical to shoulder 4 of member 3, 103, 123, 203 inorder to secure the assembly of member 3, 103, 123, 203-part 5, 105,205-locking element 9, 109, 129, 209.

FIGS. 1 and 2 also show that locking element 9, 109, 129, 209 includesan upper surface 11 intended to come into contact with a preferably flattool 15 and a lower surface 12 intended to come into contact with theupper surface of part 5, 105, 205.

Indeed, as explained below, surprisingly, the axial stress exerted byperipheral portion 13 of locking element 9, 109, 129, 209 in the methoddoes not cause any breakage of the second material which has little orno plastic domain. This technical advantage makes it possible toconsiderably simplify the assembly of part 5, 105, 205 onto, for examplea pivoting staff 2, 102, 122, 202. This advantage is obtained, inparticular since peripheral portion 13 of locking element 9, 109, 129,209 bears on shoulder 4 and not in a cantilevered position with respectto shoulder 4. It is therefore important that the surface of lockingelement 9, 109, 129, 209 does not exceed that of shoulder 4.

In the example illustrated in FIGS. 1 and 2, locking element 9 issymmetrical, i.e. surfaces 11 and 12 may be either the upper or lowersurface. However, this symmetry is merely optional and preferablyapplied to prevent handling errors during manufacture.

The elastic assembly of locking element 9, 109, 129, 209 isadvantageously obtained by using a third material which includes a metalor a metal alloy whose resistance to relaxation is equal to at least 50%of the applied force. Tests for determining this percentage were carriedout after 10,000 hours at a temperature of 70° C. and under a force of75% of the stress necessary to obtain 0.2% plastic deformation, i.e.substantially 75% of the elastic limit of the third material.

Resistance of more than 50% was observed when the third materialincludes copper, brass, nickel silver (also called “maillechort” or “newsilver”), ARCAP alloy, and even more than 85% when the third materialincludes Pfinodal alloy, Spinodal alloy, Durnico alloy, Durimphy alloy,Cu—Be alloy and 20AP steel.

For considerations specific to horology, locking element 9, 109, 129,209 is, even more preferably, chosen from among the above materialswhich do not possess ferromagnetic properties, to be insensitive tomagnetic fields, i.e., copper, brass, nickel silver (also called“maillechort” or “new silver”), ARCAP alloy, Pfinodal alloy, Spinodalalloy, Cu—Be alloy and Durimphy alloy.

As better illustrated in FIGS. 1 and 2, preferably according to theinvention, the height H to width L ratio (H/L) of locking element 9,109, 129, 209 in cross-section in an axial plane is between 0.1 and 5.Thus, it is important to properly select length L to obtain a peripheralportion 13 which is sufficiently far from the centre of axis D to obtaina sufficiently high lever arm to offer sufficient clamping to secure anassembly together. At the same time, a height H must also be properlyselected in order to obtain a minimum height to sufficiently protect thesecond material having little or no plastic domain, and a maximum heightto still obtain the intermediate deformation explained below. It istherefore understood that ratio H/L must be adapted to the anticipatedapplication.

According to another preference, locking element 9, 109, 129, 209 ischamfered to prevent any breakage of the second material which haslittle or no plastic domain. Indeed, as explained below, depending onthe geometry of the intermediate deformation, a chamfer may preventlocking element 9, 109, 129, 209 from entering into contact on the uppersurface of part 5, 105, 205 via a sharp edge capable of generatingexcessive stress and/or pressure on a minimal surface.

Thus, advantageously according to the invention, said at least firstmaterial formed for member 3, 103, 123, 203 may include a large varietyof materials, such as, for example, a metal or a metal alloy.

The method of manufacturing a first embodiment of assembly system 1according to the invention illustrated in FIG. 9 is explained below withreference to FIGS. 3 to 8.

The method includes a first step a) consisting in forming each portionof assembly system 1. Thus, step a) includes a phase intended to form amember 3 made of at least a first material including a staff 2 and ashoulder 4 which may or may not be in a single piece, a second phaseintended to form a part 5 made of a second material having lithe or noplastic domain such as, for example, a silicon-based material, with anaperture 6 and a third phase intended to form a locking element 9 in theform of a washer made of a third material and whose hole 8 is smallerthan staff 2 or member 3. It is understood that in step a), the order ofexecution of the phases is of no importance.

The method continues with a second step b) consisting in passing staff 2of member 3 freely into aperture 6 of part 5. Step b) is illustrated inFIG. 4.

Step c) continues the method and includes a first phase intended toplace staff 2 against hole 8 in locking element 9. This first phase ofstep c) is also illustrated in FIG. 4. A tool 15 is also observed inFIG. 4. This tool 15 is preferably flat, i.e. has a substantially flatsurface 14 intended to come into contact with upper surface 11 oflocking element 9. It is thus noted that if locking element 9 issymmetrical as illustrated in FIGS. 1 and 2, assembly errors betweenupper surface 11 and lower surface 12 are eliminated.

Step c) continues with a second phase intended to forcibly slide lockingelement 9 against staff 2 using tool 15 so as to deform locking element9 so that the peripheral portion 13 of locking element 9 is the closestto part 5 as illustrated in FIG. 5. It is clear that this second phasecould be likened to a driving in operation.

This intermediate elastic deformation, which may cause isolated plasticdeformations on internal wall 10, gives the impression that lockingelement 9 is a Belleville washer. However, this geometry is not stable,i.e. it is not a plastic deformation such as creep, and is caused solelyby the force of tool 15. This intermediate elastic deformation ismaximised by the use of hole 8 in locking element 9 which is smallerthan staff 2 of member 3 and the use of tool 15 whose surface 14 issubstantially flat.

This intermediate elastic deformation is of very great importance forthe future assembly system 1 in that it applies the future axial stressto part 5 as illustrated in FIG. 6, not as close as possible to staff 2but, via the lever arm of width L of locking element 9, on theperipheral portion 13 of locking element 9. It is thus understood thatthe cross-section of shoulder 4 of member 3 should preferably besubstantially equal to or greater than that of locking element 9 toallow peripheral portion 13 to exert an axial elastic force vertical toshoulder 4 of member 3.

The method ends simply with step d) consisting in stopping and removingtool 15 when a predefined force less than the yield strength of thethird material is reached between tool 15 and shoulder 4 of member 3.Indeed, once elastic clamping has been achieved between peripheralportion 13 of locking element 9 vertical to shoulder 4 of member 3, tool15 is used to move internal wall 10 as close as possible to part 5without exceeding, on peripheral portion 13, the yield strength of thethird material used for locking element 9.

It is thus clear that, once tool 15 has been removed, it is notdesirable for the entire width L of lower surface 12 of locking element9 to exert a stress against part 5 but only, or mainly, on peripheralportion 13 thereof. The securing of the member 3-part 5-locking element9 assembly is thus achieved only or mainly by an axial elastic force ofperipheral portion 13 of locking element 9 vertical to shoulder 4 ofmember 3, combined with the radial gripping of inner wall 10 of lockingelement 9 against staff 2 of member 3.

FIG. 3 is a graphical representation of the force applied by tool 15 inthe above method according to the axial position of tool 15. From arrowA, the second phase of step c) starts as illustrated in FIG. 5. Fromarrow B, peripheral portion 13 of locking element 9 starts to clamp part5 as illustrated in FIG. 6. From arrow C, internal wall 10 of lockingelement 9 is moved as close as possible to part 5 as illustrated in FIG.7 and any additional force from tool 15 exerts an internal stress onlocking element 9 with no impact on the geometry of locking element 9.

It is therefore clear that the steps of the manufacturing method and theelements of the assembly system are very simple and easy to implement.Thus, according to a first embodiment illustrated in FIG. 9, it ispossible to fix a balance spring 5 to a balance staff 2, by using anassembly system 1 of the invention. To achieve this, the collet 7 ofbalance spring 5 is secured between pivot 3 and locking element 9.

In order to minimise the risk of plastic deformation of locking element9, 109, 129, 209, step d) is stopped when the force applied by tool 15is comprised between 20% and 90% of the yield strength of the thirdmaterial. Of course, the percentage must be adapted according to theanticipated application. During tests, it became clear that stoppingstep d) is entirely satisfactory when the force applied by tool 15 issubstantially equal to 75% of the yield strength of the third material.

As explained above, the elastic assembly of locking element 9, 109, 129,209 is advantageously obtained by using a third material which includesa metal or a metal alloy whose resistance to relaxation is equal to atleast 50% of the applied force. Tests for determining this percentagewere carried out after 10,000 hours at a temperature of 70° C. and undera force of 75% of the stress necessary to obtain 0.2% plasticdeformation.

Resistance of more than 50% was observed when the third materialincludes copper, brass, nickel silver (also called “maillechort” or “newsilver”), ARCAP alloy, and even more than 85% when the third materialincludes Pfinodal alloy, Spinodal alloy, Durnico alloy, Durimphy alloy,Cu—Be alloy and 20AP steel.

For considerations specific to horology, locking element 9, 109, 129,209 is, even more preferably, chosen from among the above materialswhich do not possess ferromagnetic material, so as to be insensitive tomagnetic fields, i.e., copper, brass, nickel silver (also called“maillechort” or “new silver”), ARCAP alloy, Pfinodal alloy, Spinodalalloy, Cu—Be alloy and Durimphy alloy.

As better illustrated in FIGS. 1 and 2, preferably according to theinvention, the height H to width L ratio (H/L) of locking element 9,109, 129, 209 in cross-section in an axial plane is between 0.1 and 5.Thus, it is important to properly select length L to obtain a peripheralportion 13 which is sufficiently far from the centre of axis D to obtaina sufficiently high lever arm to offer sufficient clamping to secure anassembly together. At the same time, the height must also be properlyselected in order to obtain a minimum height to sufficiently protect thesecond material having little or no plastic domain, and a maximum heightto still obtain the intermediate deformation explained below. It istherefore understood that ratio H/L must be adapted to the anticipatedapplication.

According to another preference, locking element 9, 109, 129, 209 ischamfered to prevent any breakage of the second material. Indeed, asexplained above, depending on the geometry of the intermediatedeformation, a chamfer may prevent locking element 9, 109, 129, 209 fromentering into contact on the upper surface of part 5, 105, 205 via asharp edge capable of generating excessive stress on a minimal surface.

Thus, advantageously according to the invention, said at least one firstmaterial formed for member 3, 103, 123, 203 may include a large varietyof materials, such as, for example, a metal or a metal alloy. It is thusunderstood that staff 2, 102, 122, 202 and shoulder 4 may be in a singlepiece using a single first material or that staff 2, 102, 122, 202 andshoulder 4 of member 3, 103, 123, 203 may be formed of several materialsand/or several portions.

It is also understood that, as a result of the method of the invention,the second material having little or no plastic domain may include, inparticular, silicon, quartz, corundum, silicon oxide, silicon nitride orsilicon carbide with no risk of breakage.

FIG. 10 shows other embodiments of assembly systems 101, 121, 201according to the invention within the field of horology. Pallets 105, byway of example, may include two assemblies 101, 121 according to theinvention, respectively for securing the dart 103 and pin 123 to thepallet-lever 107.

As shown in FIG. 10, each assembly system 101, 121 includes pallet-lever107 which is secured between staff 102 of the dart 103 or staff 122 ofthe pin 123 and locking element 109, 129. It is thus clear that eachassembly system 101, 121 is sufficiently resistant to avoid generatingrelative movements between its components.

In the same Figure, an escape wheel, and more generally wheel 205includes, by way of example, an assembly system 201 intended to secure apivot 203 to wheel 205. As shown in FIG. 10, assembly system 201includes a hub 207 which is secured between staff 202 of pivot 203 andlocking element 209.

It is thus immediately clear that the example assembly system 201 can beapplied to any type of wheel set. Further, pin 203 may comprise a pinionin a single part to form a complete wheel set.

Of course, this invention is not limited to the illustrated example butis capable of various variants and alterations that will appear to thoseskilled in the art. In particular, locking element 9, 109, 129, 209 canhave a different geometry without departing from the scope of theinvention.

Tool 15 could also include a substantially conical surface 14 tosubstantially follow the Belleville washer shape obtained during theintermediate elastic deformation.

Further, aperture 6 in part 5, 105, 205 is not limited to a circularshape and/or part 5, 105, 205 may be partially pierced below lockingelement 9, 109, 129, 209. Thus, by way of example, balance spring 5 ofFIG. 9 could be replaced by the balance spring 10 including a collet 41whose aperture is substantially trefoil-shaped of EP Patent No 2363762which is incorporated by reference in the present patent application,without losing any of the aforecited advantages.

Finally, different “fragile” materials from silicon or alumina basedmaterials may be envisaged, such as, for example, zirconium or titaniumbased ceramics, or glass. Locking element 9, 109, 129, 209 may also beformed from a base of amorphous metals also called metallic glasses.

What is claimed is:
 1. An assembly system comprising: a member made ofat least a first material including a staff and a shoulder, the staff ofthe member being received in the aperture of a part made of a secondmaterial, wherein the assembly system includes a locking element made ofa third material arranged to elastically attach the part between theshoulder of said member and the locking element, and wherein the lockingelement is a washer whose internal wall radially grips the staff of saidmember and, after the washer is moved to contact the part in order tosecure the member-part-locking element assembly, the washer iselastically deformed to exert an axial force to the shoulder of saidmember that is larger along peripheral portions of the washer than atradially inward portions of the washer, and wherein the second materialis silicon-based.
 2. The assembly system according to claim 1, whereinthe third material includes a metal or a metal alloy whose resistance torelaxation, after 10,000 hours at a temperature of 70° C. is equal to atleast 50% of the applied force representing 75% of the stress necessaryto obtain 0.2% plastic deformation of the third material in order tomaintain the secure assembly of the member-part-locking element.
 3. Theassembly system according to claim 2, wherein the third materialincludes copper, brass, and/or nickel silver.
 4. The assembly systemaccording to claim 1, wherein the height (H) to width (L) ratio (H/L) ofthe locking element in cross-section in an axial plane is between 0.1and
 5. 5. The assembly system according to claim 1, wherein the lockingelement is chamfered to prevent any breakage of the second material. 6.The assembly system according to claim 1, wherein the second materialincludes silicon, quartz, silicon oxide, silicon nitride or siliconcarbide.
 7. The assembly system according to claim 1, wherein said atleast one first material includes a metal or a metal alloy.
 8. Theassembly system according to claim 1, wherein the staff and the shoulderare in a single piece.
 9. A timepiece wherein the timepiece includes atleast one assembly system according to claim
 1. 10. The timepieceaccording to claim 9, wherein the part made of a second material is awheel set, pallets or a balance spring.
 11. A method of manufacturing anassembly system comprising the following steps: forming a member made ofat least a first material including a staff and a shoulder, a part madeof a second material with an aperture and a locking element in a form ofa washer made from a third material and whose hole is smaller than thestaff of said member; passing the staff of said member freely into theaperture of the part; placing the staff against the hole in the lockingelement and forcibly sliding the locking element against the staff usinga tool to elastically deform the locking element so that the peripheralportion of the locking element is closest to the part; and stopping andremoving said tool when a predefined force less than the yield strengthof the third material is reached between the tool and the shoulder ofsaid member, and wherein the second material is silicon-based.
 12. Themethod according to claim 11, wherein the stopping and removing isstopped when the force applied by said tool is comprised between 20% and90% of the yield strength of the third material.
 13. The methodaccording to claim 11, wherein the third material includes a metal or ametal alloy whose resistance to relaxation, after 10,000 hours at atemperature of 70°C. is equal to a least 50% of the force applied in thestopping and removing representing 75% of the stress necessary to obtain0.2% plastic deformation of the third material in order to maintain thesecure assembly of the member-part-locking element.
 14. The methodaccording to claim 13, wherein the third material includes copper,brass, and/or nickel silver.
 15. The method according to claim 11,wherein the height (H) to width (L) ratio (H/L) of the locking elementin cross-section in an axial plane is between 0.1 and
 5. 16. The methodaccording to claim 11, wherein the locking element is chamfered toprevent any breakage of the second material.
 17. The method according toclaim 11, wherein the second material includes silicon, quartz, siliconoxide, silicon nitride or silicon carbide.
 18. The method according toclaim 11, wherein said at least first material includes a metal or ametal alloy.
 19. The method according to claim 11, wherein the part is atimepiece wheel set.
 20. The method according to claim 11, wherein thepart is pallets of a timepiece.
 21. The method according to claim 11,wherein the part is a timepiece balance spring.